The prior art comprises many folding carriage structures most of which are collapsible. See, e.g., U.S. Pat. No. 3,390,893 by Maclaren et al. The difficulty with the prior art devices is that the two side brace elements surround and confine on both sides a passenger in the seat resulting in a very uncomfortable and unnatural seated position. Further, only a toggle bar at the rear of the seat is provided for carriage support. The legs, and in particular, the knee joints of the passenger are forced to rest against the lower edge of a bucket-like seat, which is formed of a material such as woven plastic. This is also a disadvantage resulting in an even more confined and unnatural seated position.